When I bring up the friends tab in front of the main steam window, and try to click on anything within the tab, it disappears behind the steam window. I have to close down all other windows before i can operate the friends tab. This happens in both Ubuntu 12.04 - Unity and in Linux Mint - Cinnamon. Please comment if you've experienced this.

I have the same issue. Friends list window should be placed above other windows when it is bringing up. This issue also appears in menu:View -> FriendsView -> ServersView -> ScreenshotsView -> SettingsSteam -> Settings